In the walking control of a biped humanoid robot, the walking performance is seriously affected by the initial home posture. An important thing is that the initial home posture of real robot is slightly different at every setting because a zero position of joint is not exactly the same. Accurate and consistent initial home posture is essential when we compare and analyze walking control algorithms. In general, the conventional method for electric motor uses an incremental encoder with a limit switch or an absolute encoder such as potentiometer to make a zero position. However, this method for the multi-axis humanoid robot is difficult, time-consuming, and inaccurate. Furthermore, it has the disadvantage that additional limit switch or absolute encoder can interfere with the design objective of compactness. This paper describes a novel adjustment method of home posture for a humanoid robot utilizing incremental encoders, an inertial sensor and force torque sensors. Four kinds of controllers are proposed and adjusted offsets are measured when outputs of the controllers are converged. The experimental results from KHR-2 show the effectiveness of the proposed algorithm.

This work presents three online controllers for maintaining dynamic stability of a humanoid robot using force/torque sensor. Those are damping controller, landing orientation controller and landing position controller. The legs of a humanoid robot are relatively long and serially connected with compliant force/torque sensor at the ankle. This architecture has the inherent characteristics of a lightly damped system. Most research on balance control overlook the deterministic vibration caused by structural compliance. In addition, the vibration was not positively considered to improve the characteristics of the system. Therefore, a simple inverted pendulum model with compliant joint is proposed. For this model, the damping controller that increases system damping is proposed as a balance controller. Furthermore, the performance of maintaining balance against external forces is experimentally shown. A landing orientation controller at the ankle joints is presented to manage fast and stable ground contact. A landing position controller is implemented in order to modify the prescribed trajectory of the swing foot and to reduce the landing impact during unexpected landing. The effectiveness of the proposed controllers is confirmed by walking experiments that has been applied on the KAIST humanoid robot platform KHR-1.

Since conventional above-knee prostheses are passive type devices with constant mechanical properties, the knee joint motions are not similar to that of normal persons. On the other hand, active type prostheses can improve the swing phase gait but these are expensive, heavy and consume large energy. Thus we propose a semi-active prosthesis using the rotary magnetorheological (MR) damper. The torque dissipation in the knee joint can be controlled by the magnetic field induced by the solenoid. A 3-DOF leg simulator has been developed to generate various hip motions and analyze the results of walking motions. The tracking control of knee joint angle was performed with this leg simulator. The experiment shows that the proposed prosthesis system has good performance in swing phase. We applied the repetitive controller in conjunction with the computed control law and PD control law. This algorithm reduces the RMS tracking error as the repetitions of the tracking. Moreover, the proposed prosthesis system is adaptable to walking speed.